JBL M2 Reference Master Monitor Review

[Absolute]

I haven't looked at the perceived similarities but if it were a measurement rig issue then every other speaker would show the same behavior. Aside from that, this speaker was measured on its side. The HTM-12 was measured vertically.

But, to top it off, I do sanity checks with a groundplane measurement on larger speakers like this. They match. Otherwise I don't post the data until I figure out what is wrong. And those groundplane measurements are taken with a completely different microphone, too.

IOW, the chance is 0.00%.

How do you ensure sufficient decoupling between the speaker and the base it's standing on when measured?
Is it possible with large speakers to change their resonant behaviour depending on whether they stand or lay down on the base?

 

[pos]

Took some nearfield measurements of my other two M2s to (hopefully) even further rule out it being a bad sample.
Attach files
View attachment 149775
View attachment 149776

The woofer seems to track Erin's pretty well
View attachment 149777

I just now realized the close mic measurement experiment we did on audioheritage involved your speakers!
If you have access to the DSP settings could you try replacing the 3 EQ points around 250Hz with the ones listed here? http://www.audioheritage.org/vbulle...erence-Monitor&p=392375&viewfull=1#post392375

 

[Blumlein 88]

How do you ensure sufficient decoupling between the speaker and the base it's standing on when measured?
Is it possible with large speakers to change their resonant behaviour depending on whether they stand or lay down on the base?

Yes of course. Those that lay down, have an easy, relaxed, suave sound that reminds one of James Bond as played by Sean Connery. Those that stand straight up resonate in a way that reminds you of the "Pink Panther" detective.

 

[Absolute]

Yes of course. Those that lay down, have an easy, relaxed, suave sound that reminds one of James Bond as played by Sean Connery. Those that stand straight up resonate in a way that reminds you of the "Pink Panther" detective.

It's a valid question because you are effectively changing the mass of the side panel by laying it down on its side.

I'm no engineer, so I wonder if the resonances will be the same when standing on 4 contact points on its feet versus laying down on the platform on its side and, if not, whether this is taken into account in some way.

 

[hardisj]

It's a valid question because you are effectively changing the mass of the side panel by laying it down on its side.

I'm no engineer, so I wonder if the resonances will be the same when standing on 4 contact points on its feet versus laying down on the platform on its side and, if not, whether this is taken into account in some way.

the impedance sweep with DATS was done when the speaker had already been taken off the stand. And it showed an unmistakable resonance around 270Hz compared to the woofer alone without said resonance.

this also shows up in @synthetic’s NF measurements posted previously.

 

[Absolute]

the impedance sweep with DATS was done when the speaker had already been taken off the stand. And it showed an unmistakable resonance around 270Hz compared to the woofer alone without said resonance.

this also shows up in @synthetic’s NF measurements posted previously.

The huge resonance at 270ish is beyond question and shows up everywhere, even in my own clones, it's just the overall jagged response between 100-500hz that seemed strange. Looks almost like ripples on a quiet lake that shouldn't be there. Hence my question if there's a possibility that there's some other reason than those main culprits at 270 and 500 hz.

What I can clearly see from your measurements is that I need to take a look at my own ports. Mine are resonating like crazy at 680 hz measured at close range.

Looks like I'll have some work to do.

 

[Zvu]

Have you printed constant radius ports from JBL or you used something else ?

 

[PatentLawyer]

Am I seeing this correct? I have been in a lot of expensive homes/apartments and haven't seen a 20k cubic foot theater. That is basically a 30 x 45 x 15 room. Maybe the closest and it might have been over was one Cineramax on AVS did about a decade ago. IIRC it was three or four stepped levels of seating and a 20 foot wide screen.

The biggest theater I can ever recall was by Arnold Chase in Connecticut. IIRC it was 100 seats. There was a thread at Curt Palme. The owner participated as well.

The CT one, was it on Conyers Chase in Greenwich, by any chance? If so, that's one of the specific ones I have in mind.

 

[Absolute]

Have you printed constant radius ports from JBL or you used something else ?

It's some kind of Aero ports, so not like the originals.

 

[Jim Matthews]

Am I seeing this correct? I have been in a lot of expensive homes/apartments and haven't seen a 20k cubic foot theater. That is basically a 30 x 45 x 15 room.

I would venture a SWAG that most of us pursuing this as a hobby are lucky to have the back of one chair as a closet, and *maybe* a reclaimed attic Spider Condo as a dedicated listening space.

Some of the rooms described are bigger than my first house.

 

[Ericglo]

The CT one, was it on Conyers Chase in Greenwich, by any chance? If so, that's one of the specific ones I have in mind.

http://www.curtpalme.com/forum/viewtopic.php?t=6521&postdays=0&postorder=asc&&start=0

Here is the thread over at Curts. I would have to read through it to find out where it is located. I remember Arnold saying the theater wasn't just for movie watching. He was going to host fund raisers and the like with the theater as an audiotrium.

I would venture a SWAG that most of us pursuing this as a hobby are lucky to have the back of one chair as a closet, and *maybe* a reclaimed attic Spider Condo as a dedicated listening space.

Some of the rooms described are bigger than my first house.

The two bigger ones that I can think of over at AVS are Art Sonneborns and Rob Hahns. I am not sure if they get to 20k ft cubed.
https://keithyates.com/portfolio/hahn-theater/

I was in a $40 mill house a couple of years ago that had a nice HT, but it wasn't big. Most of the HTs that I see in these houses aren't huge. I do go into more apartments, which obviously would not have something that large. Probably the most expensive and biggest was the Zaha Hadid building. One of the penthouses is $25 mill. It was big, but I couldn't see where one could put a large HT

 

[Zvu]

It's some kind of Aero ports, so not like the originals.

Well, won't you be surprised then

https://www.thingiverse.com/thing:2446845

 

[synthetic]

I just now realized the close mic measurement experiment we did on audioheritage involved your speakers!
If you have access to the DSP settings could you try replacing the 3 EQ points around 250Hz with the ones listed here? http://www.audioheritage.org/vbulle...erence-Monitor&p=392375&viewfull=1#post392375

You got it.

Here is what that should look like applied to the listening window from Erin's data.

It creates a pretty big dip at 287Hz since his data didn't actually show the 282Hz resonance as a peak for some reason.

Without the new filters:

 

[JWAmerica]

Lots of drivers big and small have a surround related dip, the size of the driver affecting where it will appear. Most of the Faital Pro drivers have a similar dip.

View attachment 149792

Troels Graveson uses a technique where he applies an adhesive on half the surround. Scanspeak does the same on their top of line midrange.
http://www.troelsgravesen.dk/Edge-coating.htm
SB made a pure midrange driver with a foam surround to eliminate it. Purifi uses their funky looking surround to avoid it. Another one of those things that looks worse than it sounds, although there is often a peak in distortion where there is a dip in FR.

This reminds me of the Insignia NS-B2111 that were briefly popular. Edge coating the woofer was a popular tweak to smooth out the response.

https://www.speakerdesign.net/midrange_tweaks/insignia/insignia_woofer.html

Are people still applying various substances to their speakers in the current year?

 

[pos]

You got it. (...)

Thanks!
I guess this can really differ from one unit to another.
Luckily this is pretty easy to measure and adjust on sight.

 

[synthetic]

@pos You may be interested to know that Erin also measured your rePhase settings on my OpenDRC and the only substantial difference seems to be the MiniDSP tweeter looks 0.6 - 1dB lower (to its benefit, imo).

If I want to improve the response using Erin's data, will the OpenDRC have enough taps to start with your filters and add additional ones? Or would it be better to subtract out your preset from Erin's measurement and start from scratch?

 

[pos]

@pos You may be interested to know that Erin also measured your rePhase settings on my OpenDRC and the only substantial difference seems to be the MiniDSP tweeter looks 0.6 - 1dB lower (to its benefit, imo).

Interesting indeed, thanks for posting this!
Did not realize the speaker tested by Erin was also yours!
The rephase settings found in the google doc are adjusted to a fraction of a dB based on the measurement of actual BSS devices, which might differ from the Crown amp used in Erin's measurement. I never got around measuring the actual output of one of these Crown amp.
For one thing the Crown amp and the amp you are using with the openDRC might react differently to the impedance rise in the UHF (albeit a minimal one, thanks to the passive lpad).
Another possible reason would be a small gain difference between the two channels of either (or both) amps, or even possible DACs.
The best way to deal with this parameter would be to measure the actual output of the amp with a multi-meter and adjust gains accordingly.
This is of course especially true if you are using different amps (or DACs) for the woofer and the compression driver.

If I want to improve the response using Erin's data, will the OpenDRC have enough taps to start with your filters and add additional ones? Or would it be better to subtract out your preset from Erin's measurement and start from scratch?

I would definitely adjust using the existing rephase settings, possibly canceling some specific EQ points (like the ones around 250Hz) to start from scratch in these specific areas only. That is already what I did when adjusting the original preset based on measurements of BSS units, and this can be seen as I used different EQ banks for that part.

Contrary to analog EQs, and even digital IIR/biquad ones, with FIR/convolution you can use as many EQ points as you want without advert effects (noise, distortion and what not). What matters are the resulting magnitude and phase target curves, regardless of the EQ points used to obtain them. So you might want to chose the easiest path.

Regarding taps limitations, the original rephase settings are already at the limit of what the openDRC can do on the LF side, especially on that 21Hz EQ. If you need to do some additional LF EQs (based on Erin's measurement, or on measurement of your own speaker/room system) you might want to use the IIR section of the openDRC for these.

I'd be curious to hear your opinion once you can compare the flat HF response vs the original one. I have a feeling that dip at 6.5kHz might be there for a reason (has to be, right! right?...), although I must admit I struggle to understand what it would be. I chose to let that alone on my own system, but might change my mind based on your report

 

[Lorenzo74]

Hold your horses there, cowboy. Just because I'm posting here and Amir has unblocked my site... I'm not sure we are quite there yet.

you should be both proud to deliver such high value to the audio community like nobody else on the planet. Amir has created a magic place. (To me @amirm either you will hire someone to increase the number of speaker reviews, or you will end up with partnering with a good fellow).

Let’s image for a while, the full hifi products with focus on dac and amp covered by Amir on the west coast, south east by @hardisj with a deep dive on speakers, drivers, planets and stars… and maybe one day the east coast supported by audio knowledge holder, the honorable professor @John Atkinson…

the very place for audio-music lover, the last mile, the high end Nirvana where knowledge is cultivated nurtured and spread for sake of progress…
best luck good boys!
let’s team up!

(edited)

 

[Ron Texas]

Let’s image for a while, the full hifi products with focus on dac and amp covered by Amir on the east coast, the central America by @hardisj with a deep dive on speakers, drivers, planets and stars… and maybe one day the east coast supported by audio knowledge holder, the honorable professor @John Atkinson…

Your geography is way off. Amir is on the West Coast. Erin is in the Southeast. Central America is not in the USA.

 

[Lorenzo74]

Your geography is way off. Amir is on the West Coast. Erin is in the Southeast. Central America is not in the USA.

too late here, forgive me…
indeed Amir is on the west Coast and Alabama according to timezone in central (US of) America, make sense?

however many thanks, I edited the post.